In product distribution channels such as product shipping, a Styrofoam packing material has been used for a long time for packing commodity and industrial products. Although the styrofoam package material has a merit such as a good thermal insulation performance and a light weight, it has also various disadvantages: recycling the styrofoam is not possible, soot is produced when it burns, a flake or chip comes off when it is snagged because of it's brittleness, an expensive mold is needed for its production, and a relatively large warehouse is necessary to store it.
Therefore, to solve such problems noted above, other packing materials and methods have been proposed. One method is a fluid container of sealingly containing a liquid or gas such as air (hereafter also referred to as an “air-packing device”). The air-packing device has excellent characteristics to solve the problems involved in the styrofoam. First, because the air-packing device is made of only thin sheets of plastic films, it does not need a large warehouse to store it unless the air-packing device is inflated. Second, a mold is not necessary for its production because of its simple structure. Third, the air-packing device does not produce a chip or dust which may have adverse effects on precision products. Also, recyclable materials can be used for the films forming the air-packing device. Further, the air-packing device can be produced with low cost and transported with low cost.
FIG. 1 shows an example of structure of an air-packing device in the conventional technology. The air-packing device 20 includes a plurality of air containers 22 and check valves 24, a guide passage 21 and an air input 25. The air from the air input 25 is supplied to the air containers 22 through the air passage 21 and the check valves 24. Typically, the air-packing device 20 is composed of two thermoplastic films which are bonded together at bonding areas 23a. 
Each air container 22 is provided with a check valve 24. One of the purposes of having multiple air containers with corresponding check valves is to increase the reliability, because each air container is independent from the others. Namely, even if one of the air containers suffers from an air leakage for some reason, the air-packing device can still function as a shock absorber for packing the product because other air containers are still inflated due to the corresponding check valves.
FIG. 2 is a plan view of the air-packing device 20 of FIG. 1 when it is not inflated which shows bonding areas for closing two thermoplastic films. The thermoplastic films of the air-packing device 20 are bonded (heat-sealed) together at bonding areas 23a which are rectangular periphery thereof to air tightly close the air-packing device 20. The thermoplastic films of the air-packing device 20 are also bonded together at bonding areas 23b which are boundaries of the air containers 22 to air-tightly separate the air containers 22 from one another.
When using the air-packing device, each air container 22 is filled with the air from the air input 25 through the guide passage 21 and the check valve 24. After filling the air, the expansion of each air container 22 is maintained because each check-valve 24 prevents the reverse flow of the air. The check valve 24 is typically made of two small thermoplastic films which are bonded together to form an air pipe. The air pipe has a tip opening and a valve body to allow the air flowing in the forward direction through the air pipe from the tip opening but the valve body prevents the air flow in the backward direction.
Air-packing devices are becoming more and more popular because of the advantages noted above. There is an increasing need to store and carry precision products or articles which are sensitive to shocks and impacts often involved in shipment of the products. There are many other types of product, such as wine bottles, DVD drivers, music instruments, glass or ceramic wares, antiques, etc. that need special attention so as not to receive a shock, vibration or other mechanical impact. Thus, it is desired that the air-packing device protects the product to minimize the shock and impact. In case the product to be protected has a pointed end, the possibility exists that the air-packing device may be ruptured by it. Thus, it is also desired that the air-packing device does not rupture during transportation.